Affective disorder are common, severe, recurrent, heterogeneous psycniatric diseases with an elusive pathophysiology. Their clinical and etiological complexity may obscure efforts to uncover mechanisms and tc discover therapeutic agents against those mechanisms. One common clinical feature that heightens complexity is comorbid anxiety. Combined anxiety and affective disorder syndromes exacerbate functional morbidity and suffering of patients, but may also present an opportunity to discover shared etiologic factors The candidate for this career development award is an academic psychiatrist at a teaching hospital with a strong historical commitment to medical research. The candidate has already established a reputation as a clinical specialist in affective disorders and has a research background in the genetics of affective disorder; by the end of the award period he plans to have established firmly a clinical and research direction aimed a comorbid anxiety and affective disorders, with fluency in psychophysiological methods. The award will facilitate this process by providing the time and resources to pursue further training in psychophysiology, neuroscience, and genetics. The starting points for the proposed research are 1) epidemiological findings that bipolar and panic disorders commonly occur together (comorbid risk), 2) symptom provocation studies ir panic disorder that reveal latent panic vulnerability in relatives of panic disorder patients (familial risk), and 3 family study results that show both familial and comorbid risk for panic disorder. The research program proposed here will address further questions about the relationship of panic and bipolar disorders by the use of carbon dioxide inhalation to provoke panic symptoms in study subjects ascertained for genetic linkage study of bipolar disorder. Risk of panic response to carbon dioxide in subjects without prior panic disorder will be analyzed as a function of familial and comorbid risk (as compared to the risk in positive and negative control subjects). If there is a specific genetic risk factor for both bipolar and panic disorder in a subset of families, then familial and comorbid risk will interact to produce higher risk of provoked panic than will either risk factor alone. Results of this work will then be applied to ongoing genetic studies of bipolar disorder, and will inform the candidate's further research into affective and anxiety disorder etiology.